Influence of Bacteria on Body Weight
Results of a recent twin study suggest that our genes play a huge role in what types of bacteria we have in our gut. This study, specifically, is the first to determine that different types of gut microbes are heritable and that their variation is not solely influenced by diet, lifestyle, environment, and overall health. What is even more interesting, is that the abundance of this bacteria may largely influence our body weight. Genetic Analysis of Gut Microbiota in Twins Research teams from Cornell University in New York and King’s College in London sequenced the genes of microbes present in over 1,000 fecal samples taken from 416 pairs of twins in a UK data registry. Of those twins, 171 pairs were identical, sharing 100% of their genes, leaving 245 non-identical, sharing about 50% of their genes. Through 16S rRNA amplification by PCR and the PICRUSt method, results reveal that identical twins have a much more similar abundance of certain types of gut bacteria than non-identical twins. This means that genes influence the kinds of bacteria present in the gut. Types of heritable gut bacteria include families Methanobacteriaceae ''and ''Christensenellaceae as well as firmicutes of Ruminococcacaea ''and ''Lachnospiraceae ''families. Even further, researchers found that the presence of bacteria ''Christensenellaceae ''was the most influenced by genetics, possessing a very high heritability. One strain, ''Christensenellaceae minuta ''was observed as more common among individuals with a lower body weight. When introducing the bacteria to mice guts, it was found that the mice gained less weight than those who did not receive the bacteria. This suggests that increasing amounts of ''Christensenellaceae minuta ''in the human gut could help to reduce or even prevent obesity. Bacteriodetes were also found in high amounts among twins, however their lack of heritability suggest they are strongly influenced by environmental factors. However, they have also been shown to respond to diet interventions (1). Other Studies Many other studies have also touched upon the correlation between gut bacteria and obesity, however they all present different theories. This past September, a study was released suggesting that Granny Smith apples could help fight obesity by helping to balance the proportions of “good” gut bacteria. Researchers from Washington State University explain that the specific fibers and polyphenols present in Granny Smith apples are unharmed by stomach acid and other digestive components by the time they reach the colon. The bacteria in the colon can then ferment these compounds and produce the butyric acid that triggers the growth of good bacteria (3). Another study from this past July explains the creation of a probiotic capable of preventing obesity. Researchers fromVanderbilt University were able to genetically modify a strain of normal gut flora, ''Escherichia coli Nissle 1917, to produce a compound known as N-acyl-phosphatidylethanolamine (NAPE), which can help to reduce overall food intake. After administering this bacteria to mice guts, the mice were fed high-fat diets for 8 weeks. Afterword, the team found that it significantly reduced their food intake, body fat, and fatty liver, compared to the control mice (4). Useful Applications These results may open the door to specific probiotic treatments that could help to reduce the risk of obesity and its related diseases. Increasing certain strains of bacteria, specifically Christensenellaceae minuta, in the gut could reduce or prevent obesity. Researchers in China have also found that higher levels of toxin-producing bacteria, such as enterobacteria within the gut can lead to insulin resistance. As a result, the host would not feel full after one portion of food. Instead, they need many more in order to feel full. The body will not tell the host it is satisfied. Altering the levels of this bacteria could help to promote genes which help the body to burn fat. If the same host were fed a resitrictive diet, they would still be unable to lose weight because their gut would still contain the same bacteria, deactivating the genes that promote fat burning (4). By knowing which bacteria contribute to metabolism and fat burning and overall sense of fullness, we are able to alter their expression in order to promote a healthier lifestyle through weight loss and obesity prevention. References 1. Goodrich J., et al. "Human Genetics Shape the Gut Microbiome". Cell Journal. Nov. 6 2014. 1;4. pp. 789-799. 2. "Could an apple a day protect against obesity?" Medical News Today. Sep. 2014. 3. "Could a probiotic prevent obesity?" Medical News Today. July 2014. 4. Stephens P. "Weight loss: Is the secret in your bacteria?" BBC News. April 2014.